To select a helical bevel gearbox for a mixer or agitator, start with the actual operating conditions—not motor power alone. Define the required output speed and torque, the material being mixed, the duty cycle, the starting and peak loads, the installation arrangement, and the operating environment. Then check that the gearbox’s rated mechanical capacity, thermal capacity, ratio, mounting configuration, and output shaft can handle those conditions. At WGT, we recommend sending these details to your gearbox supplier before confirming a model, especially when the process involves high viscosity, frequent starts, or changing batch conditions.
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A helical bevel gearbox combines helical gearing with bevel gearing to transmit power through an angle, commonly between perpendicular input and output shafts. In a mixer drive, it reduces motor speed and increases available output torque so the impeller can operate at the speed required by the process. Its right-angle arrangement can also help fit a drive into a layout where a directly aligned motor and mixer shaft would be impractical. The exact benefits depend on the gearbox design, selected ratio, mounting position, and application loads.
Describe what the mixer handles, including the liquid or material, its viscosity range, solids content, and whether the process changes as mixing proceeds. A drive that starts in a thin liquid may face a different load from one that must start with a settled or highly viscous batch. Note whether the mixer runs continuously, in batches, intermittently, or with frequent starts and stops. If the load varies, share the normal and worst-case operating conditions rather than providing only an average.
Also identify the impeller type, tank arrangement, and shaft orientation. These details help the supplier understand the load path and whether the gearbox output will experience radial or axial forces in addition to transmitted torque. Where those forces are significant, the gearbox’s permissible loads and any need for separate shaft support should be reviewed. Do not assume that the gearbox alone should carry every force from the mixer assembly.
Provide the motor’s rated power, rated speed, electrical supply details, and starting method if known. State the required mixer output speed, including any speed range needed for different recipes or process stages. The approximate reduction ratio is the input speed divided by the required output speed. For example, reducing an input of 1,450 rpm to 30 rpm requires an approximate ratio of 48.3:1; the supplier should confirm the available ratio and resulting actual output speed.
Torque is central to gearbox selection because it describes the twisting force available at the output shaft. For a basic estimate using metric units, output torque in newton-metres can be calculated as 9,550 multiplied by power in kilowatts and divided by speed in revolutions per minute. For example, 7.5 kW at 30 rpm gives an ideal calculated torque of approximately 2,388 N·m before accounting for losses or application factors. Treat this as a preliminary calculation, not as a gearbox rating or a substitute for supplier review.
Ask the supplier to check the required torque against the gearbox’s rated mechanical capacity and thermal capacity. Mechanical capacity concerns the loads the gear components can transmit, while thermal capacity concerns heat dissipation under the specified operating conditions. A gearbox may need a different selection if it runs continuously, operates in a hot environment, or experiences frequent starts. Share the actual duty cycle and ambient conditions so these checks use relevant assumptions.
Mixers can produce peak loads during startup, when a batch is settled, or when the material becomes more resistant to movement. Explain how often these conditions occur and how long they last. A service factor may be used in selection, but its appropriate value depends on the gearbox manufacturer’s method and the specific application. As an illustration only, applying a factor of 1.5 to a calculated 2,388 N·m would produce a design check value of about 3,582 N·m; this is not a universal requirement or a recommended rating for every mixer.
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Confirm how the drive will be mounted, the direction of the input and output shafts, and the available space around the tank. Check the required output shaft form, coupling or hollow-shaft arrangement, and the connection to the mixer shaft. The mounting position can affect lubrication and heat management, so it must match the gearbox manufacturer’s approved installation instructions. Include a drawing or clear layout description when possible.
Review the operating environment as part of the same decision. Consider exposure to moisture, washdown, dust, chemicals, outdoor conditions, and ambient temperature. Specify any enclosure or corrosion-resistance requirements instead of assuming that a standard configuration will suit a demanding environment. If the gearbox is installed near a food, pharmaceutical, or chemical process, clarify the applicable plant requirements with your engineering and procurement teams.
A gearbox should be selected as part of the complete drive, not as an isolated component. Verify that the motor and gearbox are compatible in power, speed, mounting, and connection, and confirm whether a variable-frequency drive or other speed-control method will be used. If speed changes over a wide range, ask the supplier to assess both torque availability and thermal performance across the operating range. Also check that the mixer shaft, coupling, support structure, and tank arrangement can accommodate the expected loads.
Review the maintenance and operating requirements before ordering. Confirm the lubricant specification, inspection intervals, installation instructions, and any planned spare-parts needs with the supplier. Where production depends on the mixer, ask what documentation and technical support can be provided for installation and commissioning. Clear expectations at this stage can reduce avoidable fit-up or operating issues.
A complete inquiry helps a supplier make a more useful recommendation and identify missing information early. Provide the motor power and speed, desired output speed or range, estimated torque if available, duty cycle, batch characteristics, and startup conditions. Include the installation orientation, shaft and mounting requirements, environmental conditions, and any drawing or photograph that clarifies the layout. If a current gearbox is being replaced, share its nameplate details and explain what prompted the change.
Ask the supplier to state the selected ratio, output speed, rated torque, service-factor assumptions, thermal suitability, allowable external loads, mounting arrangement, and required accessories. Request clarification where a value depends on an assumption, such as material viscosity or operating hours. This makes it easier for your engineering team to compare proposals on equivalent conditions rather than price alone. WGT can review the application information with your team and discuss a suitable helical bevel gearbox configuration for the mixer or agitator requirements.
Select a helical bevel gearbox by matching the process load, required speed, torque, duty cycle, installation geometry, and environment to verified gearbox ratings. Use power-and-speed calculations as a starting point, then have the supplier review peak loads, thermal conditions, and external shaft forces. Do not choose a service factor or configuration by assumption; share the operating details and confirm the selection basis. For a practical next step, prepare your motor data, mixer operating conditions, mounting information, and layout drawing before requesting a quotation from WGT.
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